Meeting Abstract
An essential question on comparative cognition is what are the brain mechanisms for behavioral differences between species. Poison frogs (Dendrobates auratus) have evolved complex parental behaviors, including egg attendance and tadpole transport, which rely heavily on spatial memory. While sympatric túngara frog (Engystomops pustulosus) builds foam nests in ponds without any parental care. First, we tested their behaviors in a two-arm maze in which we provided visual cues to learn correct arm, which was rewarded with return to the home cage. Both species learned the task. However, a probe trial showed that the poison frog used spatial cues to learn the task while the túngara frog used local cues. Furthermore, when we reversed the reward-cue contingencies, we found that poison frogs learned reversal task, while túngara frogs did not. In order to study the brain mechanisms underlying these species differences in cognition, we took samples of the hippocampus (medial pallium) from naïve and trained poison frogs and from naïve túngara frogs, and sequenced their transcriptomes via RNASeq. We found that 54 genes were differentially expressed between naïve and trained poison frogs. BLAST results show that these genes facilitate neural proliferation, dendrite growth, neural survival, and synthesis of neurotransmitters and neurotrophic factors. Reciprocal BLAST between the 54 genes in poison frog and the transcriptome of naïve túngara frog detected 39 matches. More than 70% of the 39 genes show the same expression pattern between naïve and trained poison frogs as that between naïve poison frogs and naïve túngara frogs. Therefore, we conclude that these species differences in spatial cognition result, at least in part, from differential hippocampal neurogenesis.
